The process of extration, commenly used for extracting codeine from other painkillers (paracetamol, ibuprofen) it is usually combined with in legally avaliable pills. it is a fairly simple process however time consuming but necassary to get the nice codeine. i will go into detail but read no further if you've ever recreationally taken any other opiates (morphine, heroin) as codeine is a weak form and won't give you a buzz you'll OD before you get 'there'.
first get yourself some codeine and paracetamol tablets (co-codamol) then boil some water. depending on the strength of the tablets you want to empty around 300mg of codine so calculate howmany pills you need. then pour boiling water over the pills mix them into the water, then allow to cool, preferably in a fridge then filter the water using coffee filters, the liquid left will be diluted coedine without binders or paracetamol. result

'argh mate cold water extraction is effort, but its worth it'
'nah man since i had those morphine based pills codeine just don't work'
'hmmm'

A Cold Water Extraction, or CWE for short, is primarily used to separate tylenol from opiate-based pain-relievers because tylenol is known to be damaging to the liver in large doses, so CWE's are what you use when your doctor is a complete asshole and prescribes you weak pain medication. Opiates dissolve readily in cold water, while tylenol seeps to the bottom.

The CWE process goes as follows:

1. Crush up said pills (Vicodin, Percocets, etc.) into as fine of a powder as possible. You should be doing one CWE for no more than five pills at once.

2. Take about 150mL of water and bring it to a warm temperature--make sure it is not hot or the opiate will be destroyed and your efforts compromised. You should be able to stuck your finger in the water and hold it there comfortably. Think of about the same temperature as a heated pool.

3. Mix the powder in with the warm water and stir.

4. Put the glass in the freezer and let it chill for about 30 minutes.

5. Take it out and filter the water through a coffee filter into an empty glass. What you see in the bottom of the first glass in the freezer when you first take it out is the APAP. If you're doing a CWE, you don't want that, so filter through a coffee filter. Pour carefully and slowly. Make sure you have the coffee filter secured.

6. Lastly, to speed up the process, gently squeeze the coffee filter to empty any remaining water into the glass.

And you're done. The result is a slightly cloudy mixture, but will taste bitter.